The present invention relates to a corrugated disposable diaper. The diaper is formulated with an initially molten film and elastic in such a manner as to firmly stabilize the absorbent batt and subject the batt to corrugation.
Disposable diapers have become commercially important. The structure of these diapers is similar and generally has three basic elements: a liquid-impermeable backing, an absorbent batt, and a liquid-permeable facing. Generally, the backing is of a film such as a polyethylene film. Typical prior art diapers are shown in U.S. Pat. Nos. Re. 26,151 and 3,612,055. Generally, the absorbent batt is smaller in size than the backing or the facing and is sandwiched between the backing and facing, the latter two being laminated one to the other in the marginal portions and substantially coextensive with one another. Frequently, the absorbent batt is a fluff batt of loosely-compacted cellulosic fibers such as wood pulp fibers.
The backing film, typically a polyethylene film, though it is liquid-impermeable, is frequently noisy. Furthermore, the film has a slick feeling to it. Attempts have been made to overcome these drawbacks. For instance, a diaper having a fibrous outer layer is shown in U.S. Pat. No. 3,779,246. While diapers formed in accordance with this patent have improved feel and appearance as compared to diapers having an exposed plastic sheet as the outermost layer, the additional fabric layer coupled with the necessary adhesive introduces additional thickness which in turn can impair flexibility.
Another problem with commercially available disposable diapers is the stability of the fluff batt. Many improvements have been made to stabilize the fluff batt. For instance in U.S. Pat. No. 3,017,304, a paper-like densified skin is provided on the outermost side of the fluff batt, and in U.S. Pat. No. 3,938,522 densified regions, generally in the form of embossed lines, are present to both stabilize the fluff batt and to promote wicking. Whereas these techniques resulted in an improved product, the paper-like densified skin and/or the densified regions tend to stiffen the fluff batt, and it is known that the densified regions are of reduced liquid-holding capacity. All of the known disposable diaper products are laminated products wherein adhesive or glue is required to adhere one layer of the product to another. The adhesive or glue also lends thickness to the product and hence, can make the product less flexible. Furthermore, the adhesive or glue detracts from the absorbent capacity of the product.
An attempt was made to produce a glueless product in U.S. Pat. No. 2,897,108. Tissue sheets were arranged in a stepped fashion, symmetrically one above the other, whereby marginal areas of each successive tissue sheet extended beyond the counterpart edge of the next smaller tissue sheet. A continuous liquid-impermeable plastic film is extrusion coated onto the stacked tissue sheets so as to be coextensive in area with the largest tissue sheet. The film extends across and in contact with the outwardly facing surface of the smallest tissue sheet and the successive marginal areas of the larger tissue sheets and is bonded at least at selected areas to each of the contact tissue sheets. The articles produced by the patent have not met with commercial success for a variety of reasons. First of all, the article is so thin as to be fragile. Secondly, absorbency is entirely inadequate because the tissue sinks into and becomes integral with the film causing substantial loss of potential absorbency. In essence, the product formed by the patent is a sheet of conventional commercially available tissue to which a thin coating of plastic material is applied. The paper-like feel and extremely limited absorptive capacity renders such a product unacceptable as a disposable absorbent product in today's marketplace.
Another problem related to disposable diapers has been the sealing of the diaper about the legs of the wearer, generally, an infant. Elastic has been placed in the leg regions in an attempt to prevent leakage of the diaper. For example, U.S. Pat. Nos. 3,860,003, 4,050,462, and 4,324,245 provide for placement of elastic in the central portion of the diaper in order to assist the diaper in conforming to the leg of the infant. Though a diaper with elastic in the central portion in the margins may improve the fit about the leg, the problem with leakage still exists.
There remains the unsolved need in the marketplace for a disposable diaper product having absorbency characteristics at least equal to those of presently available disposable products, a conformable, comfortable fit, a cloth-like feel, and a product which can be produced by less complex and less expensive processing equipment.